This invention relates to a heat sensitive recording sheet which has excellent adaptability to various printers and facsimiles and further can provide clear copies by various copying devices.
Since heat sensitive recording system has many characteristics such as non-impact type which generates little noise at recording, no need of development and fixation, simple maintenance, etc., the system has been used for many purposes such as various printers and facsimiles and furthermore, labels, tickets, etc.
Heat sensitive recording sheets used for these purposes are prepared so that they have the characteristics suitable for respective uses and in many cases, not only the heat printed information images are read, but copies are produced therefrom by a copying device or the printed images are sent via facsimile. More specifically, copying systems include various types such as silver salt type, diazo type, electrostatic type, etc., but the main office copying systems now employed are electrostatic types, among which the most popular is the PPC type. However, the diazo type has also high utilization because of low cost and convenience. Further, most of the facsimile devices are provided with copying function.
In order to read thermal printed information images, to make copies from the images by PPC type copying system or to make copies or send the images via facsimile, the images as original must be high in opaqueness, otherwise the device may mistake stains in the portion contacting the backside of the original or color of platen roll for images, resulting in the problems that the stains are also copied or the whole area is printed in black.
On the other hand, when copying is carried out by the diazo type copying system, a long exposure is required to obtain clear images unless opaqueness of the images is low to some extent.
Further, the optical sensors provided in most of facsimile devices for detection of original or recording sheet may make errors unless the opaqueness of original or recording sheet is high to some extent.
When stiffness of recording sheet, especially that of in longitudinal direction is high, it sometimes becomes impossible to lead the top edge of the recording sheet to the desired position during travelling between conveying rolls in the device, resulting in paper sticking.
Problems such as poor printability, curling, etc. are also undesired.
Hitherto, there have been no heat sensitive recording sheets free from these problems.